<!doctype html>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
<canvas id="myCanvas" style="border:1px solid;" width="300" height="300"></canvas>
<script type="text/javascript">
var canvas = document.getElementById("myCanvas");  
var context = canvas.getContext('2d');  
var n = 0;  
var dx = 150;  
var dy = 150;  
var s = 100;  
context.beginPath();  
context.fillStyle = 'rgb(100,255,100)';  
context.strokeStyle = 'rgb(0,0,100)';  
var x = Math.sin(0);  
var y = Math.cos(0);  
var dig = Math.PI / 15 * 11;  
for(var i = 0; i < 30; i++) {  
	var x = Math.sin(i * dig);  
	var y = Math.cos(i * dig);  
	context.lineTo( dx + x * s,dy + y * s);  
}     
context.closePath();  
context.fill();  
context.stroke();  
</script>
</body>
</html>  
